Large aircraft are often provided with a number of multi-axle landing gear. For example, such a landing gear may comprise a bogie beam carrying three axles, each axle carrying a plurality of wheels. It is common for one of the axles, generally the rear axle, to be steerable so as to reduce tyre wear when the aircraft is taxiing. The steerable axle is generally pivotally connected to the bogie beam. An actuator provided between the bogie beam and the steerable axle can control the orientation of the axle relative to the bogie beam.
As will be appreciated, there are instances where it is desirable for a steerable axle of a landing gear to be locked in a predetermined orientation. For example, during take-off and landing it is desirable that the steerable axle is locked in an orientation which is generally orthogonal with respect to the bogie beam and parallel with respect to the other axles on the bogie beam. Such landing gears are therefore provided with a locking device for locking the orientation of the steerable axle relative to the bogie beam.
A known way of providing a locking device is to provide a locking actuator. For example, the steering actuator may be configured to lock when it is at a predefined extension state, corresponding to the extension state required to provide the desired locking orientation of the axle.
A further known locking device is to provide a slot extending into the steerable axle in a manner substantially orthogonal with respect to the longitudinal axis of the axle. A wedge may be provided that is movable between a first position where the wedge is housed within the slot, so as to prevent the steerable axle pivoting about the bogie, and a second position where the wedge is removed from the slot, to allow the axle to pivot.
Both the above-mentioned types of locking device suffer from a disadvantage in that locking elements must move into mating recesses in order for the locks to function, and move out again in order to release the locks. Such operation may be at risk of jamming, and may create noise in operation.